The average weight of a certain number of students in a group is 54 kg. if 12 students of average weight 52 kg join the group, then the average weight of all the students in the group decreases by 750 g. what was the number of students, initially in the group?
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 20
Let the number of students be x
Average = Sum of all observations/Total number of observations
The average weight of a certain number of students in a group is 54 kg
Sum of weight of x students = 54x
if 12 students of average weight 52 kg join the group, then the average weight of all the students in the group decreases by 750 g
New average = 54 - 0.75 = 53.25kg
Sum of weight of 12 students = 52 × 12 = 624kg
Sum of weight of all students = 624 + 54x = (x + 12) × 53.25
0.75x = 639 - 624 = 15, x = 15/0.75 = 20